1. Field of the Invention
The present invention relates to a liquid crystal display and a manufacture method thereof, particularly to a reflection type liquid crystal display provided with a thin film transistor and a manufacture method thereof.
2. Description of the Prior Art
A so-called active matrix type liquid crystal display provided with switching elements such as thin film transistors is constituted of a thin film transistor substrate (hereinafter referred to as the TFT substrate) in which a plurality of thin film transistors are arranged in a matrix manner, and an opposite substrate provided with a transparent common electrode and disposed opposite to the TFT substrate via a liquid crystal layer. In a color liquid crystal display, a color filter layer is formed on either the TFT substrate or the opposite substrate.
Moreover, the color liquid crystal display is largely classified into a reflection type liquid crystal display using a pixel electrode on the side of the TFT substrate formed of an opaque reflective metal, and a transmission type liquid crystal display using a transparent pixel electrode.
When the color filter layer is formed on the side of the TFT substrate, as compared with when the color filter layer is formed on the side of the opposite substrate, no overlap margin of the TFT and opposite substrates is necessary, the aperture ratio can be increased, and brighter display can be performed, which is a preferable mode. Examples of the formation of the color filter layer on the side of the TFT substrate include the transmission type liquid crystal display as disclosed in Japanese Patent Application Laid-Open No. 72473/1995 and the reflection type liquid crystal display as disclosed in Japanese Patent Application Laid-Open No. 254696/1996.
In the former transmission type liquid crystal display, in which the pixel electrode is transparent, even if the color filter layer is disposed on the side of the TFT substrate, the transparent pixel electrode can be disposed on the side of the liquid crystal. Therefore, only little influence is exerted to the electric field applied to the liquid crystal. In the latter reflection type liquid crystal display, however, since the reflective pixel electrode has to be formed below the color filter layer, the interval between the common electrode on the side of the opposite substrate and the pixel electrode is broadened by the thickness of the color filter layer, and the electric field applied to the liquid crystal is weakened, which causes a problem that the liquid crystal drive efficiency is lowered.
Moreover, the transmission type liquid crystal display and the reflection type liquid crystal display are different not only in the constituting conditions of the pixel electrode, but also in the position in which the pixel electrode is formed. When the liquid crystal displays different in the manufacture processes for reasons such as the difference of the layer structure are manufactured on the same manufacture line, optimum conditions in forming the films or performing etching or the like also change, and the setting of a manufacture device has to be changed. Since the setting change requires much time, the production efficiency is remarkably deteriorated. Moreover, since the manufacture device of the liquid crystal display is very expensive, the addition of the manufacture device to eliminate the setting change-over results in a manufacture cost increase.
Furthermore, as a special example, as disclosed in Japanese Patent Application Laid-Open No. 29787/1996, the liquid crystal display which can be applied to both the transmission type and the reflection type has also been proposed. This proposal comprises employing a color development layer including a fluorescent material to obtain a brighter color filter than the conventional color filter, forming the color development layer on a reflective layer even in the reflection type, and forming the transparent pixel electrode on the color development layer.
However, even in such reflection type liquid crystal display, the reflective layer is newly disposed using a metal different from the wiring metal of the thin film transistor in a separate process, and the manufacturing of the reflection type liquid crystal display and the transmission type liquid crystal display using the same manufacture line is not considered at all.